DDS-4 tape drive compatiblity - Ubuntu

This is a discussion on DDS-4 tape drive compatiblity - Ubuntu ; I was given two used SCSI DDS-4 tape drives, and I am testing them for use in making backups. One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq SDT-10000 (EOD006, . I find that each ...

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Thread: DDS-4 tape drive compatiblity

  1. DDS-4 tape drive compatiblity

    I was given two used SCSI DDS-4 tape drives, and I am testing them for
    use in making backups.

    One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    SDT-10000 (EOD006, .

    I find that each drive can read the tapes that it writes, but that
    neither drive can read the tapes written by the other.

    I have put a cleaning tape through each drive, and the firmware of each
    drive is up-to-date. Both drives pass the diagnostics in the HP Library
    & Tape Tool.

    Shouldn't these drives be able to read each other's tapes? Do I need to
    adjust some parameters, or should I assume that at least one of them is
    defective?

  2. Re: DDS-4 tape drive compatiblity

    On 2008-05-18, Matt hit the keyboard and wrote:
    > I was given two used SCSI DDS-4 tape drives, and I am testing them for
    > use in making backups.
    >
    > One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    > SDT-10000 (EOD006, .
    >
    > I find that each drive can read the tapes that it writes, but that
    > neither drive can read the tapes written by the other.
    >
    > I have put a cleaning tape through each drive, and the firmware of each
    > drive is up-to-date. Both drives pass the diagnostics in the HP Library
    > & Tape Tool.
    >
    > Shouldn't these drives be able to read each other's tapes? Do I need to
    > adjust some parameters, or should I assume that at least one of them is
    > defective?


    One would think that if they are both the same version
    they should be able to read each others tapes. I had a
    Video-player (still got it) when I recorded tapes with it,
    the content of the show/movie would all be in color (if the
    source was in color) yet when I played the tape in another
    player they were black/white. I tried those tapes on several
    players with the same result.



    Dragomir Kollaric
    --
    This signature is licensed under the GPL and may be
    freely distributed as long as a copy of the GPL is included... :-)


  3. Re: DDS-4 tape drive compatiblity

    Are you using the same software to test each?

    "Matt" wrote in message
    news:4KWXj.234$Vf.88@fe093.usenetserver.com...
    >I was given two used SCSI DDS-4 tape drives, and I am testing them for use
    >in making backups.
    >
    > One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    > SDT-10000 (EOD006, .
    >
    > I find that each drive can read the tapes that it writes, but that neither
    > drive can read the tapes written by the other.
    >
    > I have put a cleaning tape through each drive, and the firmware of each
    > drive is up-to-date. Both drives pass the diagnostics in the HP Library &
    > Tape Tool.
    >
    > Shouldn't these drives be able to read each other's tapes? Do I need to
    > adjust some parameters, or should I assume that at least one of them is
    > defective?




  4. Re: DDS-4 tape drive compatiblity

    I'm testing using tar and diff for both. Also using the same SCSI
    adapter and the same computer for both. I test with only one tape drive
    installed at a time.

    I test whether drive 1 can read the tape it has written, then I shut
    down, swap drives, and try to read the same tape with drive 2 and find
    that it can't read it.

    Bill wrote:
    > Are you using the same software to test each?
    >
    > "Matt" wrote in message
    > news:4KWXj.234$Vf.88@fe093.usenetserver.com...
    >> I was given two used SCSI DDS-4 tape drives, and I am testing them for use
    >> in making backups.
    >>
    >> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >> SDT-10000 (EOD006, .
    >>
    >> I find that each drive can read the tapes that it writes, but that neither
    >> drive can read the tapes written by the other.
    >>
    >> I have put a cleaning tape through each drive, and the firmware of each
    >> drive is up-to-date. Both drives pass the diagnostics in the HP Library &
    >> Tape Tool.
    >>
    >> Shouldn't these drives be able to read each other's tapes? Do I need to
    >> adjust some parameters, or should I assume that at least one of them is
    >> defective?


  5. Re: DDS-4 tape drive compatiblity

    My bet is the HP is not compatible with anything else.

    "Matt" wrote in message
    news:EFYXj.1378$ZB5.382@fe087.usenetserver.com...
    > I'm testing using tar and diff for both. Also using the same SCSI adapter
    > and the same computer for both. I test with only one tape drive installed
    > at a time.
    >
    > I test whether drive 1 can read the tape it has written, then I shut down,
    > swap drives, and try to read the same tape with drive 2 and find that it
    > can't read it.
    >
    > Bill wrote:
    >> Are you using the same software to test each?
    >>
    >> "Matt" wrote in message
    >> news:4KWXj.234$Vf.88@fe093.usenetserver.com...
    >>> I was given two used SCSI DDS-4 tape drives, and I am testing them for
    >>> use in making backups.
    >>>
    >>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>> SDT-10000 (EOD006, .
    >>>
    >>> I find that each drive can read the tapes that it writes, but that
    >>> neither drive can read the tapes written by the other.
    >>>
    >>> I have put a cleaning tape through each drive, and the firmware of each
    >>> drive is up-to-date. Both drives pass the diagnostics in the HP Library
    >>> & Tape Tool.
    >>>
    >>> Shouldn't these drives be able to read each other's tapes? Do I need to
    >>> adjust some parameters, or should I assume that at least one of them is
    >>> defective?




  6. Re: DDS-4 tape drive compatiblity

    [Crossposts removed and Followup set to a.o.l.u]

    Matt wrote:
    > I was given two used SCSI DDS-4 tape drives, and I am testing them for
    > use in making backups.
    >
    > One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    > SDT-10000 (EOD006, .
    >
    > I find that each drive can read the tapes that it writes, but that
    > neither drive can read the tapes written by the other.
    >
    > I have put a cleaning tape through each drive, and the firmware of
    > each drive is up-to-date. Both drives pass the diagnostics in the HP
    > Library & Tape Tool.
    >
    > Shouldn't these drives be able to read each other's tapes? Do I need
    > to adjust some parameters, or should I assume that at least one of
    > them is defective?



    Assume nothing without considering that neither is defective or they
    wouldn't be able to write then read the tapes. IOW, they work as
    designed, eh.

    You don't expect two different manufacturer's drives to be identical do
    you? Remember Betamax and VHS?

    These drives could differ in many ways, like signal level, protocol,
    encryption, tape speed, and especially the modulation scheme, etc.

    If they have a hardware problem, then you may have a head alignment
    difference between the two. Each can read its own tapes because it
    created them, but they cannot read the tapes written by the other unit
    because the track data is not aligned the same. Quite common in the
    audio world, and even VHS.

    One or possibly both heads are misaligned. Whether you can adjust these
    is unknown. I suspect the design engineer presumed most people would
    simply use one drive per person, or per PC, and not need to read tapes
    written on a different PC.

    My suggestion is to leave well-enough alone since they are presently
    working fine.


    --
    John

    No Microsoft, Apple, Intel, Trend Micro, nor Ford products were used in the preparation or transmission of this message.

    The EULA sounds like it was written by a team of lawyers who want to tell me what I can't do. The GPL sounds like it was written by a human being, who wants me to know what I can do.

  7. Re: DDS-4 tape drive compatiblity

    Matt writes:

    > I was given two used SCSI DDS-4 tape drives, and I am testing them for
    > use in making backups.
    >
    > One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    > SDT-10000 (EOD006, .
    >
    > I find that each drive can read the tapes that it writes, but that
    > neither drive can read the tapes written by the other.
    >
    > I have put a cleaning tape through each drive, and the firmware of
    > each drive is up-to-date. Both drives pass the diagnostics in the HP
    > Library & Tape Tool.
    >
    > Shouldn't these drives be able to read each other's tapes? Do I need
    > to adjust some parameters, or should I assume that at least one of
    > them is defective?


    DDS-4 is DDS-4, but I'm not certain that they would use the same
    hardware compression technique, if you have that enabled via the
    jumpers on the drives. You should be able to disable compression
    using "mt compression 0".

    Scott
    --
    Scott Hemphill hemphill@alumni.caltech.edu
    "This isn't flying. This is falling, with style." -- Buzz Lightyear

  8. Re: DDS-4 tape drive compatiblity

    Scott Hemphill wrote:
    > Matt writes:
    >
    >> I was given two used SCSI DDS-4 tape drives, and I am testing them for
    >> use in making backups.
    >>
    >> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >> SDT-10000 (EOD006, .
    >>
    >> I find that each drive can read the tapes that it writes, but that
    >> neither drive can read the tapes written by the other.
    >>
    >> I have put a cleaning tape through each drive, and the firmware of
    >> each drive is up-to-date. Both drives pass the diagnostics in the HP
    >> Library & Tape Tool.
    >>
    >> Shouldn't these drives be able to read each other's tapes? Do I need
    >> to adjust some parameters, or should I assume that at least one of
    >> them is defective?

    >
    > DDS-4 is DDS-4,



    I was guessing something like that. I think you are saying that the
    format is as standardize as say ext3 or fat16.


    > but I'm not certain that they would use the same
    > hardware compression technique, if you have that enabled via the
    > jumpers on the drives.



    Thanks, Scott, I'll try that. So we are expecting/hoping to be able to
    interchange any non-compressed DDS-4 tapes among DDS-4 drives.

    I found the following doc which gives a lot of technical detail on the
    Compaq (rebadged Sony) drive.

    > PRODUCT DESCRIPTION MANUAL
    > DDS-4 Tape Drive
    > Model : SDT-10000
    > : SDT-11000
    > Ver. 1.3 March, 2006
    > Sony Corporation


    > Data Compression For Information Interchange
    > Adaptive Coding with Embedded Dictionary, DCLZ Algorithm, June 1991
    > European Computer Manufacturers Association (ECMA-151)1


    > 4. 6 DATA COMPRESSION
    > The tape capacity is increased by compressing data prior to writing it to the tape. Data compression is a well established
    > technology for reducing the number of bits used to represent data in order to improve data transfer rate as well as reduce
    > the amount of storage space consumed by the data.
    > The SDT-10000/SDT-11000 uses the AK 8320 Data Compression IC from ASAHI KASEI MICROSYSTEMS. This
    > chip provides a powerful data compression algorithm in a very small package. The data compression used by the chip is
    > the DCLZ algorithm. DCLZ has been standardized (or is in the process of standardization) with the ANSI, ECMA and
    > ISO standards organizations. The DDS Manufacturers Group (made up of representatives from active DDS Format
    > Licensees) has agreed upon the DCLZ algorithm as the standard data compression algorithm for data interchange be-
    > tween DDS format drives.
    > The DC control page allows the host computer to enable data compression and also configure the way in which the drive
    > responds to compressed/uncompressed data boundaries on the tape.
    > Note: The DDS format allows both compressed and uncompressed data to reside on the same tape.
    > SDT-10000/SDT-11000 has a Dip switch to disable the Data Compression.
    > After power-on reset with this jumper set, data compression is disabled. However, a MODE SELECT command can
    > override the setting of this jumper.
    > After power-on reset without this Dip switch set, both data compression and data decompression are enabled. (See
    > 3.1.5)
    > The more random the data is, the less compression is possible. This is due to the fact that data compression operates on
    > the principle of reducing the redundancy in the data string and random data has very little redundancy.
    > Data compression is a very powerful and reliable method increasing data capacity and transfer rate without compromis-
    > ing data reliability.


    > Compression Algorithm:
    > The compression algorithm field indicates the compression algorithm the drive will use to process data sent to it by
    > the initiator (if the DCE bit is one).
    > The SDT-10000/SDT-11000 supports the DCLZ data compression algorithm which is identified by the value: 00 00
    > 00 20h in the compression algorithm field. A value of zero shall indicate that no compression algorithm is currently
    > selected. Any other values in this field will cause the drive to return a CHECK CONDITION status the sense key
    > shall be set to ILLEGAL REQUEST.


    > Decompression Algorithm:
    > For MODE SELECT the decompression algorithm field indicates the decompression algorithm selected by the
    > initiator for use in subsequent decompression of data encountered on the medium.
    > The SDT-10000/SDT-11000 can decompress data recorded with the DCLZ algorithm therefore this field can be set
    > to 00 00 00 20h. However, the SDT-10000/SDT-11000 is capable of automatic recognition of the compression
    > algorithm used to process the data encountered on the medium. Therefore, the drive will override the value in the
    > decompression field (if is set to zero) for a subsequent read operation when DCLZ compressed data is detected on
    > the media.


    > Note: A CHECK CONDITION will occur on the transition from uncompress to compressed if RED = 10b.
    > For the MODE SENSE command, the decompression algorithm field reflects either the algorithm selected
    > by the initiator or compression algorithm which was used to process the data most recently encountered on
    > the medium, during a read operation.
    > A value of zero shall indicate that the data encountered on the medium during the most recent read operation
    > was uncompressed.



    I haven't found anything definite yet about DCLZ for the DAT40i. More
    about that later.


  9. Re: DDS-4 tape drive compatiblity

    Matt wrote:
    > Scott Hemphill wrote:
    >> Matt writes:
    >>
    >>> I was given two used SCSI DDS-4 tape drives, and I am testing them for
    >>> use in making backups.
    >>>
    >>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>> SDT-10000 (EOD006, .
    >>>
    >>> I find that each drive can read the tapes that it writes, but that
    >>> neither drive can read the tapes written by the other.
    >>>
    >>> I have put a cleaning tape through each drive, and the firmware of
    >>> each drive is up-to-date. Both drives pass the diagnostics in the HP
    >>> Library & Tape Tool.
    >>>
    >>> Shouldn't these drives be able to read each other's tapes? Do I need
    >>> to adjust some parameters, or should I assume that at least one of
    >>> them is defective?

    >>
    >> DDS-4 is DDS-4,

    >
    >
    > I was guessing something like that. I think you are saying that the
    > format is as standardize as say ext3 or fat16.
    >
    >
    >> but I'm not certain that they would use the same
    >> hardware compression technique, if you have that enabled via the
    >> jumpers on the drives.

    >
    >
    > Thanks, Scott, I'll try that. So we are expecting/hoping to be able to
    > interchange any non-compressed DDS-4 tapes among DDS-4 drives.
    >
    > I found the following doc which gives a lot of technical detail on the
    > Compaq (rebadged Sony) drive.
    >
    >> PRODUCT DESCRIPTION MANUAL
    >> DDS-4 Tape Drive
    >> Model : SDT-10000
    >> : SDT-11000
    >> Ver. 1.3 March, 2006
    >> Sony Corporation

    >
    >> Data Compression For Information Interchange
    >> Adaptive Coding with Embedded Dictionary, DCLZ Algorithm, June 1991
    >> European Computer Manufacturers Association (ECMA-151)1

    >
    >> 4. 6 DATA COMPRESSION
    >> The tape capacity is increased by compressing data prior to writing it
    >> to the tape. Data compression is a well established
    >> technology for reducing the number of bits used to represent data in
    >> order to improve data transfer rate as well as reduce
    >> the amount of storage space consumed by the data.
    >> The SDT-10000/SDT-11000 uses the AK 8320 Data Compression IC from
    >> ASAHI KASEI MICROSYSTEMS. This
    >> chip provides a powerful data compression algorithm in a very small
    >> package. The data compression used by the chip is
    >> the DCLZ algorithm. DCLZ has been standardized (or is in the process
    >> of standardization) with the ANSI, ECMA and
    >> ISO standards organizations. The DDS Manufacturers Group (made up of
    >> representatives from active DDS Format
    >> Licensees) has agreed upon the DCLZ algorithm as the standard data
    >> compression algorithm for data interchange be-
    >> tween DDS format drives.
    >> The DC control page allows the host computer to enable data
    >> compression and also configure the way in which the drive
    >> responds to compressed/uncompressed data boundaries on the tape.
    >> Note: The DDS format allows both compressed and uncompressed data to
    >> reside on the same tape.
    >> SDT-10000/SDT-11000 has a Dip switch to disable the Data Compression.
    >> After power-on reset with this jumper set, data compression is
    >> disabled. However, a MODE SELECT command can
    >> override the setting of this jumper.
    >> After power-on reset without this Dip switch set, both data
    >> compression and data decompression are enabled. (See
    >> 3.1.5)
    >> The more random the data is, the less compression is possible. This is
    >> due to the fact that data compression operates on
    >> the principle of reducing the redundancy in the data string and random
    >> data has very little redundancy.
    >> Data compression is a very powerful and reliable method increasing
    >> data capacity and transfer rate without compromis-
    >> ing data reliability.

    >
    >> Compression Algorithm:
    >> The compression algorithm field indicates the compression algorithm
    >> the drive will use to process data sent to it by
    >> the initiator (if the DCE bit is one).
    >> The SDT-10000/SDT-11000 supports the DCLZ data compression
    >> algorithm which is identified by the value: 00 00
    >> 00 20h in the compression algorithm field. A value of zero shall
    >> indicate that no compression algorithm is currently
    >> selected. Any other values in this field will cause the drive to
    >> return a CHECK CONDITION status the sense key
    >> shall be set to ILLEGAL REQUEST.

    >
    >> Decompression Algorithm:
    >> For MODE SELECT the decompression algorithm field indicates the
    >> decompression algorithm selected by the
    >> initiator for use in subsequent decompression of data encountered
    >> on the medium.
    >> The SDT-10000/SDT-11000 can decompress data recorded with the DCLZ
    >> algorithm therefore this field can be set
    >> to 00 00 00 20h. However, the SDT-10000/SDT-11000 is capable of
    >> automatic recognition of the compression
    >> algorithm used to process the data encountered on the medium.
    >> Therefore, the drive will override the value in the
    >> decompression field (if is set to zero) for a subsequent read
    >> operation when DCLZ compressed data is detected on
    >> the media.

    >
    >> Note: A CHECK CONDITION will occur on the transition from uncompress
    >> to compressed if RED = 10b.
    >> For the MODE SENSE command, the decompression algorithm field
    >> reflects either the algorithm selected
    >> by the initiator or compression algorithm which was used to
    >> process the data most recently encountered on
    >> the medium, during a read operation.
    >> A value of zero shall indicate that the data encountered on the
    >> medium during the most recent read operation
    >> was uncompressed.

    >
    >
    > I haven't found anything definite yet about DCLZ for the DAT40i. More
    > about that later.
    >


    That's the culprit - HW compression chips differ in the compression
    algorithm used.

    Set the drives jumpers to NOT use HW compression, then use software like
    the commercial BackupEdge (www.microlite.com) with software compression
    enabled, or pipe the backup through gzip or bzip2.

    --
    ----------------------------------------------------
    Pat Welch, UBB Computer Services, a WCS Affiliate
    SCO Authorized Partner
    Microlite BackupEdge Certified Reseller
    Unix/Linux/Windows/Hardware Sales/Support
    (209) 745-1401 Cell: (209) 251-9120
    E-mail: patubb@inreach.com
    ----------------------------------------------------

  10. Re: DDS-4 tape drive compatiblity

    Pat Welch wrote:
    > Matt wrote:
    >> Scott Hemphill wrote:
    >>> Matt writes:


    >>>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>>> SDT-10000 (EOD006, .
    >>>>
    >>>> I find that each drive can read the tapes that it writes, but that
    >>>> neither drive can read the tapes written by the other.


    >>> DDS-4 is DDS-4,


    >>> but I'm not certain that they would use the same
    >>> hardware compression technique, if you have that enabled via the
    >>> jumpers on the drives.


    > That's the culprit - HW compression chips differ in the compression
    > algorithm used.
    >
    > Set the drives jumpers to NOT use HW compression,


    Thank you, Pat.

    I have docs for the Compaq drive describing how to do that, but I
    haven't been able to find good docs on the jumpers (DIP switches
    actually) for the HP DAT40i. Any specific information about that would
    be a big help.


  11. Re: DDS-4 tape drive compatiblity

    Matt wrote:
    > Pat Welch wrote:
    >> Matt wrote:
    >>> Scott Hemphill wrote:
    >>>> Matt writes:

    >
    >>>>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>>>> SDT-10000 (EOD006, .
    >>>>>
    >>>>> I find that each drive can read the tapes that it writes, but that
    >>>>> neither drive can read the tapes written by the other.

    >
    >>>> DDS-4 is DDS-4,

    >
    >>>> but I'm not certain that they would use the same
    >>>> hardware compression technique, if you have that enabled via the
    >>>> jumpers on the drives.

    >
    >> That's the culprit - HW compression chips differ in the compression
    >> algorithm used.
    >>
    >> Set the drives jumpers to NOT use HW compression,

    >
    > Thank you, Pat.
    >
    > I have docs for the Compaq drive describing how to do that, but I
    > haven't been able to find good docs on the jumpers (DIP switches
    > actually) for the HP DAT40i. Any specific information about that would
    > be a big help.
    >


    See if this helps (took me a while to find it on HP's site):

    Data compression - Switches 1 and 2
    Switches 1 and 2 are used to configure the way in which data compression
    is set for the drive. The following table shows the available options:

    Switch 1 Switch 2 Meaning
    On On Compression enabled at power-on, with host control

    On Off Compression enabled at power-on, no host control

    Off On Compression disabled at power-on; the host is allowed
    to control compression

    Off Off Compression disabled at power-on, no host control

    *
    If Switch 1 is ON, data written to the tape will be compressed
    without the knowledge of the host.
    *
    If Switch 2 is ON, data compression can be controlled by the
    operating system if supported.
    *
    By default, the drive will decompress data when reading a
    compressed tape, regardless of the settings of Switches 1 and 2.
    Decompression can be turned off through choice of device file, and can
    be controlled by the operating system if supported.

    Enjoy.

    --
    ----------------------------------------------------
    Pat Welch, UBB Computer Services, a WCS Affiliate
    SCO Authorized Partner
    Microlite BackupEdge Certified Reseller
    Unix/Linux/Windows/Hardware Sales/Support
    (209) 745-1401 Cell: (209) 251-9120
    E-mail: patubb@inreach.com
    ----------------------------------------------------

  12. Re: DDS-4 tape drive compatiblity

    Bill wrote:
    > My bet is the HP is not compatible with anything else.
    >
    > "Matt" wrote in message
    > news:EFYXj.1378$ZB5.382@fe087.usenetserver.com...
    >> I'm testing using tar and diff for both. Also using the same SCSI adapter
    >> and the same computer for both. I test with only one tape drive installed
    >> at a time.
    >>
    >> I test whether drive 1 can read the tape it has written, then I shut down,
    >> swap drives, and try to read the same tape with drive 2 and find that it
    >> can't read it.
    >>
    >> Bill wrote:
    >>> Are you using the same software to test each?
    >>>
    >>> "Matt" wrote in message
    >>> news:4KWXj.234$Vf.88@fe093.usenetserver.com...
    >>>> I was given two used SCSI DDS-4 tape drives, and I am testing them for
    >>>> use in making backups.
    >>>>
    >>>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>>> SDT-10000 (EOD006, .
    >>>>
    >>>> I find that each drive can read the tapes that it writes, but that
    >>>> neither drive can read the tapes written by the other.
    >>>>
    >>>> I have put a cleaning tape through each drive, and the firmware of each
    >>>> drive is up-to-date. Both drives pass the diagnostics in the HP Library
    >>>> & Tape Tool.
    >>>>
    >>>> Shouldn't these drives be able to read each other's tapes? Do I need to
    >>>> adjust some parameters, or should I assume that at least one of them is
    >>>> defective?

    >
    >

    Is there a hardware compression built-in to one or both that can be
    defeated?

  13. Re: DDS-4 tape drive compatiblity

    Kirk C Aune wrote:
    > Bill wrote:
    >> My bet is the HP is not compatible with anything else.
    >>
    >> "Matt" wrote in message
    >> news:EFYXj.1378$ZB5.382@fe087.usenetserver.com...
    >>> I'm testing using tar and diff for both. Also using the same SCSI
    >>> adapter and the same computer for both. I test with only one tape
    >>> drive installed at a time.
    >>>
    >>> I test whether drive 1 can read the tape it has written, then I shut
    >>> down, swap drives, and try to read the same tape with drive 2 and
    >>> find that it can't read it.
    >>>
    >>> Bill wrote:
    >>>> Are you using the same software to test each?
    >>>>
    >>>> "Matt" wrote in message
    >>>> news:4KWXj.234$Vf.88@fe093.usenetserver.com...
    >>>>> I was given two used SCSI DDS-4 tape drives, and I am testing them
    >>>>> for use in making backups.
    >>>>>
    >>>>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>>>> SDT-10000 (EOD006, .
    >>>>>
    >>>>> I find that each drive can read the tapes that it writes, but that
    >>>>> neither drive can read the tapes written by the other.
    >>>>>
    >>>>> I have put a cleaning tape through each drive, and the firmware of
    >>>>> each drive is up-to-date. Both drives pass the diagnostics in the
    >>>>> HP Library & Tape Tool.
    >>>>>
    >>>>> Shouldn't these drives be able to read each other's tapes? Do I
    >>>>> need to adjust some parameters, or should I assume that at least
    >>>>> one of them is defective?

    >>
    >>

    > Is there a hardware compression built-in to one or both that can be
    > defeated?


    I do not know about the DDS-4 drives, but my VXA (scsi) drives have hardware
    compression that can be defeated with the _mt_ command.

    mt -f /dev/st0 compression

    compression
    (SCSI tapes) The compression within the drive can be switched on
    or off using the MTCOMPRESSION ioctl. Note that this method is
    not supported by all drives implementing compression. For
    instance, the Exabyte 8 mm drives use density codes to select
    compression.

    MTCOMPRESSION ioctl is described in the st man page.

    I am not sure this is true for all Exabyte 8mm drives as they have several
    product lines. (I always use compression, so I have never tried this.)

    Exabyte say:

    9.7 DATA COMPRESSION PAGE (PAGE CODE 0Fh)
    The Data Compression page enables you to turn data compression on or off at
    any position on the tape. To turn compression off, send this page with the
    DCE bit set to 0. To turn compression back on, send this page with the DCE
    bit set to 1.
    Bit 7 6 5 4 3 2 1 0
    Byte
    00 RSVD | Page Code
    01 Page Length
    02 DCE | DCC | Reserved
    03 DDE RED | Reserved
    04 (MSB)
    Compression Algorithm
    ...
    07 (LSB)
    08 (MSB)
    Decompression Algorithm
    ...
    11 (LSB)
    12
    Reserved
    ...
    15

    Byte 00, Bits 5 through 0 * Page Code
    The value for this field is 0Fh, identifying the current page as the Data
    Compression page.
    Byte 01 *Length This field indicates the number of bytes in the Data
    Compression page that follow this byte. The valid value for this field is
    0Eh (14 bytes).
    Byte 02, Bit 7 * DCE (Data Compression Enable This field enables or disables
    data compression, as follows:
    0 Data compression is disabled
    1 Data compression is enabled (default setting)


    --
    .~. Jean-David Beyer Registered Linux User 85642.
    /V\ PGP-Key: 9A2FC99A Registered Machine 241939.
    /( )\ Shrewsbury, New Jersey http://counter.li.org
    ^^-^^ 17:40:01 up 7:37, 4 users, load average: 4.54, 4.58, 4.43

  14. Re: DDS-4 tape drive compatiblity

    Pat Welch wrote:
    > Matt wrote:
    >> Pat Welch wrote:
    >>> Matt wrote:
    >>>> Scott Hemphill wrote:
    >>>>> Matt writes:

    >>
    >>>>>> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >>>>>> SDT-10000 (EOD006, .
    >>>>>>
    >>>>>> I find that each drive can read the tapes that it writes, but that
    >>>>>> neither drive can read the tapes written by the other.

    >>
    >>>>> DDS-4 is DDS-4,

    >>
    >>>>> but I'm not certain that they would use the same
    >>>>> hardware compression technique, if you have that enabled via the
    >>>>> jumpers on the drives.

    >>
    >>> That's the culprit - HW compression chips differ in the compression
    >>> algorithm used.
    >>>
    >>> Set the drives jumpers to NOT use HW compression,

    >>
    >> Thank you, Pat.
    >>
    >> I have docs for the Compaq drive describing how to do that, but I
    >> haven't been able to find good docs on the jumpers (DIP switches
    >> actually) for the HP DAT40i. Any specific information about that
    >> would be a big help.
    >>

    >
    > See if this helps (took me a while to find it on HP's site):
    >
    > Data compression - Switches 1 and 2
    > Switches 1 and 2 are used to configure the way in which data compression
    > is set for the drive. The following table shows the available options:
    >
    > Switch 1 Switch 2 Meaning
    > On On Compression enabled at power-on, with host control
    >
    > On Off Compression enabled at power-on, no host control
    >
    > Off On Compression disabled at power-on; the host is
    > allowed to control compression
    >
    > Off Off Compression disabled at power-on, no host control
    >
    > *
    > If Switch 1 is ON, data written to the tape will be compressed
    > without the knowledge of the host.
    > *
    > If Switch 2 is ON, data compression can be controlled by the
    > operating system if supported.
    > *
    > By default, the drive will decompress data when reading a
    > compressed tape, regardless of the settings of Switches 1 and 2.
    > Decompression can be turned off through choice of device file, and can
    > be controlled by the operating system if supported.
    >
    > Enjoy.
    >


    Thanks. I googled for some of the text you quoted and was able to find
    on the HP site only a manual for an 8GB DAT drive. However I found "HP
    DDS Drives, Edition 8, December 1999, P/N C1534-90911 at
    http://download.transtec.de/doit/loa...S_auto_eng.pdf
    which gave settings for model C5383A, which is not the model number
    stamped on my drive, but is the model number reported by my drive's BIOS.

  15. Re: DDS-4 tape drive compatiblity

    Scott Hemphill wrote:
    > Matt writes:
    >
    >> I was given two used SCSI DDS-4 tape drives, and I am testing them for
    >> use in making backups.
    >>
    >> One is an HP DAT40i (aka C5686A, C5683A) and the other is a Compaq
    >> SDT-10000 (EOD006, .
    >>
    >> I find that each drive can read the tapes that it writes, but that
    >> neither drive can read the tapes written by the other.
    >>
    >> I have put a cleaning tape through each drive, and the firmware of
    >> each drive is up-to-date. Both drives pass the diagnostics in the HP
    >> Library & Tape Tool.
    >>
    >> Shouldn't these drives be able to read each other's tapes? Do I need
    >> to adjust some parameters, or should I assume that at least one of
    >> them is defective?

    >
    > DDS-4 is DDS-4, but I'm not certain that they would use the same
    > hardware compression technique, if you have that enabled via the
    > jumpers on the drives. You should be able to disable compression
    > using "mt compression 0".
    >
    > Scott



    Thanks to everybody for your help so far.

    I set DIP switches on the drive to disable compression.

    I find that the HP DDS Drives User Manual that I mention elsewhere on
    the thread states that the DAT 40GB drive uses DCLZ compression. The
    Sony docs for the Compaq drive say that too.

    I find that both drives can read each other's tapes, but I think it was
    probably not fixed by turning off compression. It gets tedious to
    experiment, as I shut down the system when I change drives, but I will
    settle that question after a while.

    To fill in some details: Each drive reads its own tapes with ease. It
    seems the HP can read and write about 1/3 faster than the Compaq. The
    Compaq reads the HP's tapes pretty well, but the HP makes a lot of
    awful noises as if doing some kind of head-loading or positioning
    operation. I know these noises are normal for this drive, but they
    shouldn't be so frequent. Pretty clearly it is retrying a failed
    operation. In fact when I use du to look at what tar is writing on the
    disk during extraction, I can see the output files fail to grow while
    there is a lot of noise from the drive. It always succeeds eventually,
    and the data comes out exactly correct each time---for instance, I made
    the HP read and verify a tape of ten 100MB archives made by the Compaq.
    But it takes the HP a lot of noise and something like five times as
    much time to read the Compaq's tapes as it takes to read its own tapes.

    Maybe it was the compression, but I also think it may have been that the
    drives were dirty. I have used a cleaning tape on each one about five
    times.

    Another change I made was to install the mt-st package, which apparently
    has its own device drivers.

    I also have been more patient. Rather than killing the job when the
    drive makes so much noise, I am now virtually plugging my ears and
    letting it run.

    I found this text at
    http://grox.net/doc/linux/howto-OLD-...I-HOWTO-8.html


    > Problems taking tapes to/from other systems
    >
    > You can't read a tape made with another operating system or another operating system can't read a tape written in Linux.
    >
    > Different systems often use different block sizes. On a tape device using a fixed blocksize, you will get errors when reading blocks written using a different block size.
    >
    > To read these tapes, you must set the blocksize of the tape driver to match the blocksize used when the tape was written, or to variable.
    >
    > NOTE : this is the hardware block size, not the blocking factor used with tar, dump, etc.
    >
    > You can do this with the mt command -
    >
    > mt setblk
    >
    > or
    >
    > mt setblk 0
    >
    > to get variable block length support.
    >
    > Note that these mt flags are NOT supported under the GNU version of mt which is included with some Linux distributions. Instead, you must use the BSD derived Linux SCSI mt command. Source should be available from
    >
    > tsx-11.mit.edu:/pub/linux/ALPHA/scsi
    >
    > Also note that by default, ST_BUFFER_BLOCKS (defined in /usr/src/linux/drivers/scsi/st_options.h in newer kernels, st.c in older kernels) is set to allow for a 32K maximum buffer size; you'll need to edit the source to use larger blocks.



    Here is the output of mt-st -f /dev/nst0 status:

    SCSI 2 tape drive:
    File number=10, block number=0, partition=0.
    Tape block size 0 bytes. Density code 0x26 (DDS-4 or QIC-4GB).
    Soft error count since last status=0
    General status bits on (81010000):
    EOF ONLINE IM_REP_EN

    Can anybody offer any wisdom about changing the block size? I'm
    thinking maybe the two drives are using two different block sizes and
    that the Compaq firmware copes better with the difference than the HP does.

  16. Re: DDS-4 tape drive compatiblity

    John F. Morse wrote:
    > [Crossposts removed and Followup set to a.o.l.u]
    >
    > Matt wrote:


    >> I find that each drive can read the tapes that it writes, but that
    >> neither drive can read the tapes written by the other.


    > My suggestion is to leave well-enough alone since they are presently
    > working fine.



    I don't believe you've thought that through.


  17. Re: DDS-4 tape drive compatiblity

    Matt wrote:

    > John F. Morse wrote:
    >> [Crossposts removed and Followup set to a.o.l.u]
    >>
    >> Matt wrote:

    >
    >>> I find that each drive can read the tapes that it writes, but that
    >>> neither drive can read the tapes written by the other.


    Are you surprised ? Each manufacturer uses its own data format and
    track layout. I've been in situations where a manufacturer has used a
    different format on different models !

    Its called "Lock In" !

    --
    Best Regards:
    Baron.

  18. Re: DDS-4 tape drive compatiblity

    Baron wrote:
    > Matt wrote:
    >
    >> John F. Morse wrote:
    >>> [Crossposts removed and Followup set to a.o.l.u]
    >>>
    >>> Matt wrote:
    >>>> I find that each drive can read the tapes that it writes, but that
    >>>> neither drive can read the tapes written by the other.

    >
    > Are you surprised ? Each manufacturer uses its own data format and
    > track layout. I've been in situations where a manufacturer has used a
    > different format on different models !
    >
    > Its called "Lock In" !



    Do you have experience using DDS-4 tape drives?

  19. Re: DDS-4 tape drive compatiblity

    Matt wrote:
    > John F. Morse wrote:
    >> [Crossposts removed and Followup set to a.o.l.u]
    >>
    >> Matt wrote:

    >
    >>> I find that each drive can read the tapes that it writes, but that
    >>> neither drive can read the tapes written by the other.

    >
    >> My suggestion is to leave well-enough alone since they are presently
    >> working fine.

    >
    >
    > I don't believe you've thought that through.
    >



    You are entitled to your beliefs, but you might want to explain why you
    believe what you stated.


    --
    John

    No Microsoft, Apple, Intel, Novell, Trend Micro, nor Ford products were used in the preparation or transmission of this message.

    The EULA sounds like it was written by a team of lawyers who want to tell me what I can't do. The GPL sounds like it was written by a human being, who wants me to know what I can do.

  20. Re: DDS-4 tape drive compatiblity

    Matt wrote:

    > Baron wrote:
    >> Matt wrote:
    >>
    >>> John F. Morse wrote:
    >>>> [Crossposts removed and Followup set to a.o.l.u]
    >>>>
    >>>> Matt wrote:
    >>>>> I find that each drive can read the tapes that it writes, but that
    >>>>> neither drive can read the tapes written by the other.

    >>
    >> Are you surprised ? Each manufacturer uses its own data format and
    >> track layout. I've been in situations where a manufacturer has used
    >> a different format on different models !
    >>
    >> Its called "Lock In" !

    >
    >
    > Do you have experience using DDS-4 tape drives?


    Depends upon what you mean "experience" !

    In general I do whatever the client requires. Tape & tape hardware
    tends to be a long term thing ! The problems start when replacements
    can't be found and repairs become uneconomical. That is when
    businesses find that their archives are just so much junk. In terms of
    backup systems you wouldn't belive how people rely on them without
    testing that they actually work.

    --
    Best Regards:
    Baron.

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